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Bringmann A, Unterlauft JD, Barth T, Wiedemann R, Rehak M, Wiedemann P. Müller cells and astrocytes in tractional macular disorders. Prog Retin Eye Res 2021; 86:100977. [PMID: 34102317 DOI: 10.1016/j.preteyeres.2021.100977] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 05/24/2021] [Accepted: 05/26/2021] [Indexed: 02/04/2023]
Abstract
Tractional deformations of the fovea mainly arise from an anomalous posterior vitreous detachment and contraction of epiretinal membranes, and also occur in eyes with cystoid macular edema or high myopia. Traction to the fovea may cause partial- and full-thickness macular defects. Partial-thickness defects are foveal pseudocysts, macular pseudoholes, and tractional, degenerative, and outer lamellar holes. The morphology of the foveal defects can be partly explained by the shape of Müller cells and the location of tissue layer interfaces of low mechanical stability. Because Müller cells and astrocytes provide the structural scaffold of the fovea, they are active players in mediating tractional alterations of the fovea, in protecting the fovea from such alterations, and in the regeneration of the foveal structure. Tractional and degenerative lamellar holes are characterized by a disruption of the Müller cell cone in the foveola. After detachment or disruption of the cone, Müller cells of the foveal walls support the structural stability of the foveal center. After tractional elevation of the inner layers of the foveal walls, possibly resulting in foveoschisis, Müller cells transmit tractional forces from the inner to the outer retina leading to central photoreceptor layer defects and a detachment of the neuroretina from the retinal pigment epithelium. This mechanism plays a role in the widening of outer lameller and full-thickness macular holes, and contributes to visual impairment in eyes with macular disorders caused by conractile epiretinal membranes. Müller cells of the foveal walls may seal holes in the outer fovea and mediate the regeneration of the fovea after closure of full-thickness holes. The latter is mediated by the formation of temporary glial scars whereas persistent glial scars impede regular foveal regeneration. Further research is required to improve our understanding of the roles of glial cells in the pathogenesis and healing of tractional macular disorders.
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Affiliation(s)
- Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany.
| | - Jan Darius Unterlauft
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany
| | - Thomas Barth
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany
| | - Renate Wiedemann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany
| | - Matus Rehak
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany
| | - Peter Wiedemann
- Department of Ophthalmology and Eye Hospital, University of Leipzig, 04103, Leipzig, Germany
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Bringmann A, Syrbe S, Görner K, Kacza J, Francke M, Wiedemann P, Reichenbach A. The primate fovea: Structure, function and development. Prog Retin Eye Res 2018; 66:49-84. [PMID: 29609042 DOI: 10.1016/j.preteyeres.2018.03.006] [Citation(s) in RCA: 190] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 03/20/2018] [Accepted: 03/27/2018] [Indexed: 01/31/2023]
Abstract
A fovea is a pitted invagination in the inner retinal tissue (fovea interna) that overlies an area of photoreceptors specialized for high acuity vision (fovea externa). Although the shape of the vertebrate fovea varies considerably among the species, there are two basic types. The retina of many predatory fish, reptilians, and birds possess one (or two) convexiclivate fovea(s), while the retina of higher primates contains a concaviclivate fovea. By refraction of the incoming light, the convexiclivate fovea may function as image enlarger, focus indicator, and movement detector. By centrifugal displacement of the inner retinal layers, which increases the transparency of the central foveal tissue (the foveola), the primate fovea interna improves the quality of the image received by the central photoreceptors. In this review, we summarize ‒ with the focus on Müller cells of the human and macaque fovea ‒ data regarding the structure of the primate fovea, discuss various aspects of the optical function of the fovea, and propose a model of foveal development. The "Müller cell cone" of the foveola comprises specialized Müller cells which do not support neuronal activity but may serve optical and structural functions. In addition to the "Müller cell cone", structural stabilization of the foveal morphology may be provided by the 'z-shaped' Müller cells of the fovea walls, via exerting tractional forces onto Henle fibers. The spatial distribution of glial fibrillary acidic protein may suggest that the foveola and the Henle fiber layer are subjects to mechanical stress. During development, the foveal pit is proposed to be formed by a vertical contraction of the centralmost Müller cells. After widening of the foveal pit likely mediated by retracting astrocytes, Henle fibers are formed by horizontal contraction of Müller cell processes in the outer plexiform layer and the centripetal displacement of photoreceptors. A better understanding of the molecular, cellular, and mechanical factors involved in the developmental morphogenesis and the structural stabilization of the fovea may help to explain the (patho-) genesis of foveal hypoplasia and macular holes.
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Affiliation(s)
- Andreas Bringmann
- Department of Ophthalmology and Eye Hospital, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Steffen Syrbe
- Paul Flechsig Institute of Brain Research, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Katja Görner
- Paul Flechsig Institute of Brain Research, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Johannes Kacza
- Saxon Incubator for Clinical Translation (SIKT), Leipzig University, 04103 Leipzig, Germany
| | - Mike Francke
- Paul Flechsig Institute of Brain Research, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany; Saxon Incubator for Clinical Translation (SIKT), Leipzig University, 04103 Leipzig, Germany
| | - Peter Wiedemann
- Department of Ophthalmology and Eye Hospital, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany
| | - Andreas Reichenbach
- Paul Flechsig Institute of Brain Research, Medical Faculty, University of Leipzig, 04103 Leipzig, Germany.
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Miyagawa M, Nishio SY, Kumakawa K, Usami SI. Massively parallel DNA sequencing successfully identified seven families with deafness-associated MYO6 mutations: the mutational spectrum and clinical characteristics. Ann Otol Rhinol Laryngol 2015; 124 Suppl 1:148S-57S. [PMID: 25999546 DOI: 10.1177/0003489415575055] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVES To elucidate the involvement of MYO6 mutations, known to be responsible for DFNA22/DFNB37, in Japanese hearing loss patients through the use of genetic analysis. METHODS Genomic variations responsible for hearing loss were identified by massively parallel DNA sequencing (MPS) of 63 target candidate genes in 1120 Japanese hearing loss patients, and the detailed clinical features for the patients with MYO6 mutations were collected and analyzed. RESULTS Four mutations were successfully found in 7 families exhibiting autosomal dominant inheritance. All of the patients showed progressive hearing loss, but hearing type and onset age varied. Further, none of the affected patients showed any associated symptoms, such as hypertrophic cardiomyopathy or retinitis pigmentosa. CONCLUSIONS MPS is powerful tool for the identification of rare causative deafness gene mutations, such as MYO6. The clinical characteristics noted in the present study not only confirmed the findings of previous reports but provided important new clinical information.
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Affiliation(s)
- Maiko Miyagawa
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Shin-Ya Nishio
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
| | - Kozo Kumakawa
- Department of Otorhinolaryngology, Toranomon Hospital, Tokyo, Japan
| | - Shin-Ichi Usami
- Department of Otorhinolaryngology, Shinshu University School of Medicine, Matsumoto, Japan Department of Hearing Implant Sciences, Shinshu University School of Medicine, Matsumoto, Japan
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Deletion of myosin VI causes slow retinal optic neuropathy and age-related macular degeneration (AMD)-relevant retinal phenotype. Cell Mol Life Sci 2015; 72:3953-69. [PMID: 25939269 PMCID: PMC4575690 DOI: 10.1007/s00018-015-1913-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 04/20/2015] [Accepted: 04/23/2015] [Indexed: 11/16/2022]
Abstract
The unconventional myosin VI, a member of the actin-based motor protein family of myosins, is expressed in the retina. Its deletion was previously shown to reduce amplitudes of the a- and b-waves of the electroretinogram. Analyzing wild-type and myosin VI-deficient Snell’s Waltzer mice in more detail, the expression pattern of myosin VI in retinal pigment epithelium, outer limiting membrane, and outer plexiform layer could be linked with differential progressing ocular deficits. These encompassed reduced a-waves and b-waves and disturbed oscillatory potentials in the electroretinogram, photoreceptor cell death, retinal microglia infiltration, and formation of basal laminar deposits. A phenotype comprising features of glaucoma (neurodegeneration) and age-related macular degeneration could thus be uncovered that suggests dysfunction of myosin VI and its variable cargo adaptor proteins for membrane sorting and autophagy, as possible candidate mediators for both disease forms.
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Orientation of actin filaments in teleost retinal pigment epithelial cells, and the effect of the lectin, Concanavalin A, on melanosome motility. Vis Neurosci 2014; 31:1-10. [DOI: 10.1017/s0952523813000618] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
AbstractRetinal pigment epithelial cells of teleosts contain numerous melanosomes (pigment granules) that exhibit light-dependent motility. In light, melanosomes disperse out of the retinal pigment epithelium (RPE) cell body (CB) into long apical projections that interdigitate with rod photoreceptors, thus shielding the photoreceptors from bleaching. In darkness, melanosomes aggregate through the apical projections back into the CB. Previous research has demonstrated that melanosome motility in the RPE CB requires microtubules, but in the RPE apical projections, actin filaments are necessary and sufficient for motility. We used myosin S1 labeling and platinum replica shadowing of dissociated RPE cells to determine actin filament polarity in apical projections. Actin filament bundles within RPE apical projections are uniformly oriented with barbed ends toward the distal tips. Treatment of RPE cells with the tetravalent lectin, Concanavalin A, which has been shown to suppress cortical actin flow by crosslinking of cell-surface proteins, inhibited melanosome aggregation and stimulated ectopic filopodia formation but did not block melanosome dispersion. The polarity orientation of F-actin in apical projections suggests that a barbed-end directed myosin motor could effect dispersion of melanosomes from the CB into apical projections. Inhibition of aggregation, but not dispersion, by ConA confirms that different actin-dependent mechanisms control these two processes and suggests that melanosome aggregation is sensitive to treatments previously shown to disrupt actin cortical flow.
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Samuels IS, Bell BA, Sturgill-Short G, Ebke LA, Rayborn M, Shi L, Nishina PM, Peachey NS. Myosin 6 is required for iris development and normal function of the outer retina. Invest Ophthalmol Vis Sci 2013; 54:7223-33. [PMID: 24106123 DOI: 10.1167/iovs.13-12887] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the molecular basis and the pathologic consequences of a chemically induced mutation in the translational vision research models 89 (tvrm89) mouse model with ERG defects. METHODS Mice from a G3 N-ethyl-N-nitrosourea mutagenesis program were screened for behavioral abnormalities and defects in retinal function by ERGs. The chromosomal position for the recessive tvrm89 mutation was determined in a genome-wide linkage analysis. The critical region was refined, and candidate genes were screened by direct sequencing. The tvrm89 phenotype was characterized by circling behavior, in vivo ocular imaging, detailed ERG-based studies of the retina and RPE, and histological analysis of these structures. RESULTS The tvrm89 mutation was localized to a region on chromosome 9 containing Myo6. Sequencing identified a T→C point mutation in the codon for amino acid 480 in Myo6 that converts a leucine to a proline. This mutation does not confer a loss of protein expression levels; however, mice homozygous for the Myo6(tvrm89) mutation display an abnormal iris shape and attenuation of both strobe-flash ERGs and direct-current ERGs by 4 age weeks, neither of which is associated with photoreceptor loss. CONCLUSIONS The tvrm89 phenotype mimics that reported for Myosin6-null mice, suggesting that the mutation confers a loss of myosin 6 protein function. The observation that homozygous Myo6(tvrm89) mice display reduced ERG a-wave and b-wave components, as well as components of the ERG attributed to RPE function, indicates that myosin 6 is necessary for the generation of proper responses of the outer retina to light.
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Affiliation(s)
- Ivy S Samuels
- Research Service, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio
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Abstract
The encoding of auditory information with indefatigable precision requires efficient resupply of vesicles at inner hair cell (IHC) ribbon synapses. Otoferlin, a transmembrane protein responsible for deafness in DFNB9 families, has been postulated to act as a calcium sensor for exocytosis as well as to be involved in rapid vesicle replenishment of IHCs. However, the molecular basis of vesicle recycling in IHCs is largely unknown. In the present study, we used high-resolution liquid chromatography coupled with mass spectrometry to copurify otoferlin interaction partners in the mammalian cochlea. We identified multiple subunits of the adaptor protein complex AP-2 (CLAP), an essential component of clathrin-mediated endocytosis, as binding partners of otoferlin in rats and mice. The interaction between otoferlin and AP-2 was confirmed by coimmunoprecipitation. We also found that AP-2 interacts with myosin VI, another otoferlin binding partner important for clathrin-mediated endocytosis (CME). The expression of AP-2 in IHCs was verified by reverse transcription PCR. Confocal microscopy experiments revealed that the expression of AP-2 and its colocalization with otoferlin is confined to mature IHCs. When CME was inhibited by blocking dynamin action, real-time changes in membrane capacitance showed impaired synaptic vesicle replenishment in mature but not immature IHCs. We suggest that an otoferlin-AP-2 interaction drives Ca(2+)- and stimulus-dependent compensating CME in mature IHCs.
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Adaptive evolution of the myo6 gene in old world fruit bats (family: pteropodidae). PLoS One 2013; 8:e62307. [PMID: 23620821 PMCID: PMC3631194 DOI: 10.1371/journal.pone.0062307] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 03/19/2013] [Indexed: 02/05/2023] Open
Abstract
Myosin VI (encoded by the Myo6 gene) is highly expressed in the inner and outer hair cells of the ear, retina, and polarized epithelial cells such as kidney proximal tubule cells and intestinal enterocytes. The Myo6 gene is thought to be involved in a wide range of physiological functions such as hearing, vision, and clathrin-mediated endocytosis. Bats (Chiroptera) represent one of the most fascinating mammal groups for molecular evolutionary studies of the Myo6 gene. A diversity of specialized adaptations occur among different bat lineages, such as echolocation and associated high-frequency hearing in laryngeal echolocating bats, large eyes and a strong dependence on vision in Old World fruit bats (Pteropodidae), and specialized high-carbohydrate but low-nitrogen diets in both Old World and New World fruit bats (Phyllostomidae). To investigate what role(s) the Myo6 gene might fulfill in bats, we sequenced the coding region of the Myo6 gene in 15 bat species and used molecular evolutionary analyses to detect evidence of positive selection in different bat lineages. We also conducted real-time PCR assays to explore the expression levels of Myo6 in a range of tissues from three representative bat species. Molecular evolutionary analyses revealed that the Myo6 gene, which was widely considered as a hearing gene, has undergone adaptive evolution in the Old World fruit bats which lack laryngeal echolocation and associated high-frequency hearing. Real-time PCR showed the highest expression level of the Myo6 gene in the kidney among ten tissues examined in three bat species, indicating an important role for this gene in kidney function. We suggest that Myo6 has undergone adaptive evolution in Old World fruit bats in relation to receptor-mediated endocytosis for the preservation of protein and essential nutrients.
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Loubéry S, Delevoye C, Louvard D, Raposo G, Coudrier E. Myosin VI regulates actin dynamics and melanosome biogenesis. Traffic 2012; 13:665-80. [PMID: 22321127 DOI: 10.1111/j.1600-0854.2012.01342.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 02/07/2012] [Accepted: 02/09/2012] [Indexed: 12/20/2022]
Abstract
Myosin VI has been implicated in various steps of organelle dynamics. However, the molecular mechanism by which this myosin contributes to membrane traffic is poorly understood. Here, we report that myosin VI is associated with a lysosome-related organelle, the melanosome. Using an actin-based motility assay and video microscopy, we observed that myosin VI does not contribute to melanosome movements. Myosin VI expression regulates instead the organization of actin networks in the cytoplasm. Using a cell-free assay, we showed that myosin VI recruited actin at the surface of isolated melanosomes. Myosin VI is involved in the endocytic-recycling pathway, and this pathway contributes to the transport of a melanogenic enzyme to maturing melanosomes. We showed that depletion of myosin VI accumulated a melanogenic enzyme in enlarged melanosomes and increased their melanin content. We confirmed the requirement of myosin VI to regulate melanosome biogenesis by analysing the morphology of melanosomes in choroid cells from of the Snell's waltzer mice that do not express myosin VI. Together, our results provide new evidence that myosin VI regulates the organization of actin dynamics at the surface of a specialized organelle and unravel a novel function of this myosin in regulating the biogenesis of this organelle.
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Ruiz-Loredo AY, López-Colomé AM. New insights into the regulation of myosin light chain phosphorylation in retinal pigment epithelial cells. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 293:85-121. [PMID: 22251559 DOI: 10.1016/b978-0-12-394304-0.00008-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The retinal pigment epithelium (RPE) plays an essential role in the function of the neural retina and the maintenance of vision. Most of the functions displayed by RPE require a dynamic organization of the acto-myosin cytoskeleton. Myosin II, a main cytoskeletal component in muscle and non-muscle cells, is directly involved in force generation required for organelle movement, selective molecule transport within cell compartments, exocytosis, endocytosis, phagocytosis, and cell division, among others. Contractile processes are triggered by the phosphorylation of myosin II light chains (MLCs), which promotes actin-myosin interaction and the assembly of contractile fibers. Considerable evidence indicates that non-muscle myosin II activation is critically involved in various pathological states, increasing the interest in studying the signaling pathways controlling MLC phosphorylation. Particularly, recent findings suggest a role for non-muscle myosin II-induced contraction in RPE cell transformation involved in the establishment of numerous retinal diseases. This review summarizes the current knowledge regarding myosin function in RPE cells, as well as the signaling networks leading to MLC phosphorylation under pathological conditions. Understanding the molecular mechanisms underlying RPE dysfunction would improve the development of new therapies for the treatment or prevention of different ocular disorders leading to blindness.
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Affiliation(s)
- Ariadna Yolanda Ruiz-Loredo
- División de Neurociencias, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico DF, Mexico
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Abnormal circling behavior in rat mutants and its relevance to model specific brain dysfunctions. Neurosci Biobehav Rev 2010; 34:31-49. [DOI: 10.1016/j.neubiorev.2009.07.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Accepted: 07/06/2009] [Indexed: 12/16/2022]
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Lin-Jones J, Sohlberg L, Dosé A, Breckler J, Hillman DW, Burnside B. Identification and localization of myosin superfamily members in fish retina and retinal pigmented epithelium. J Comp Neurol 2009; 513:209-23. [PMID: 19137585 PMCID: PMC2785712 DOI: 10.1002/cne.21958] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Myosins are cytoskeletal motors critical for generating the forces necessary for establishing cell structure and mediating actin-dependent cell motility. In each cell type a multitude of myosins are expressed, each myosin contributing to aspects of morphogenesis, transport, or motility occurring in that cell type. To examine the roles of myosins in individual retinal cell types, we first used polymerase chain reaction (PCR) screening to identify myosins expressed in retina and retinal pigmented epithelium (RPE), followed by immunohistochemistry to examine the cellular and subcellular localizations of seven of these expressed myosins. In the myosin PCR screen of cDNA from striped bass retina and striped bass RPE, we amplified 17 distinct myosins from eight myosin classes from retinal cDNA and 11 distinct myosins from seven myosin classes from RPE cDNA. By using antibodies specific for myosins IIA, IIB, IIIA, IIIB, VI, VIIA, and IXB, we examined the localization patterns of these myosins in retinas and RPE of fish, and in isolated inner/outer segment fragments of green sunfish photoreceptors. Each of the myosins exhibited unique expression patterns in fish retina. Individual cell types expressed multiple myosin family members, some of which colocalized within a particular cell type. Because much is known about the functions and properties of these myosins from studies in other systems, their cellular and subcellular localization patterns in the retina help us understand which roles they might play in the vertebrate retina and RPE.
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Affiliation(s)
- Jennifer Lin-Jones
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
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Schirmer M, Kaiser A, Lessenich A, Lindemann S, Fedrowitz M, Gernert M, Löscher W. Auditory and vestibular defects and behavioral alterations after neonatal administration of streptomycin to Lewis rats: Similarities and differences to the circling (ci2/ci2) Lewis rat mutant. Brain Res 2007; 1155:179-95. [PMID: 17493596 DOI: 10.1016/j.brainres.2007.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Revised: 04/04/2007] [Accepted: 04/06/2007] [Indexed: 11/28/2022]
Abstract
The clinical usefulness of aminoglycoside antibiotics is limited by their ototoxicity. In rodents, damage to the inner ear is often associated with rotational behavior and locomotor hyperactivity reminiscent of such behaviors resulting from an imbalance of forebrain dopamine systems. Based on previous observations in the circling (ci2/ci2) Lewis (LEW) rat mutant, a spontaneous mutation leading to hair cell loss, deafness, impairment of vestibular functions, lateralized circling, hyperactivity and alterations in the nigrostriatal dopamine system, we have recently hypothesized that vestibular defects during postnatal development, independent of whether induced or inherited, lead to secondary changes in the dopaminergic system within the basal ganglia, which would be a likely explanation for the typical behavioral phenotype seen in such models. In the present study, we directly compared the phenotype induced by streptomycin in LEW rats with that of the ci2 LEW rat mutant. For this purpose, we treated neonatal LEW rats over 3 weeks by streptomycin, which induced bilateral degeneration of cochlear and vestibular hair cells. Following this treatment period, the behavioral syndrome of the streptomycin-treated animals, including the lateralized rotational behavior, was almost indistinguishable from that of ci2 mutant rats. However, in contrast to the ci2 mutant rat, all alterations, except the hearing loss, were only transient, disappearing between 7 and 24 weeks following treatment. In conclusion, in line with our hypothesis, vestibular defects induced in normal LEW rats led to the same phenotypic behavior as the inherited vestibular defect of ci2 mutant rats. However, with increasing time for recovery, adaptation to the vestibular impairment developed in streptomycin-treated rats, while all deficits persisted in the mutant animals. At least in part, the transient nature of the abnormal behaviors resulting from treatment with streptomycin could be explained by adaptation to the vestibular impairment by the use of visual cues, which is not possible in ci2 rats because of progressive retinal degeneration in these mutants. Although further experiments are needed to prove this hypothesis, the present study shows that direct comparisons between these two models serve to understand the mechanisms underlying the complex behavioral phenotype in rodents with vestibular defects and how these defects are compensated.
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Affiliation(s)
- Marko Schirmer
- Department of Pharmacology, Toxicology, and Pharmacy, University of Veterinary Medicine Hannover, Bünteweg 17, Hannover, Germany
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Schwander M, Sczaniecka A, Grillet N, Bailey JS, Avenarius M, Najmabadi H, Steffy BM, Federe GC, Lagler EA, Banan R, Hice R, Grabowski-Boase L, Keithley EM, Ryan AF, Housley GD, Wiltshire T, Smith RJH, Tarantino LM, Müller U. A forward genetics screen in mice identifies recessive deafness traits and reveals that pejvakin is essential for outer hair cell function. J Neurosci 2007; 27:2163-75. [PMID: 17329413 PMCID: PMC6673480 DOI: 10.1523/jneurosci.4975-06.2007] [Citation(s) in RCA: 139] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Deafness is the most common form of sensory impairment in the human population and is frequently caused by recessive mutations. To obtain animal models for recessive forms of deafness and to identify genes that control the development and function of the auditory sense organs, we performed a forward genetics screen in mice. We identified 13 mouse lines with defects in auditory function and six lines with auditory and vestibular defects. We mapped several of the affected genetic loci and identified point mutations in four genes. Interestingly, all identified genes are expressed in mechanosensory hair cells and required for their function. One mutation maps to the pejvakin gene, which encodes a new member of the gasdermin protein family. Previous studies have described two missense mutations in the human pejvakin gene that cause nonsyndromic recessive deafness (DFNB59) by affecting the function of auditory neurons. In contrast, the pejvakin allele described here introduces a premature stop codon, causes outer hair cell defects, and leads to progressive hearing loss. We also identified a novel allele of the human pejvakin gene in an Iranian pedigree that is afflicted with progressive hearing loss. Our findings suggest that the mechanisms of pathogenesis associated with pejvakin mutations are more diverse than previously appreciated. More generally, our findings demonstrate that recessive screens in mice are powerful tools for identifying genes that control the development and function of mechanosensory hair cells and cause deafness in humans, as well as generating animal models for disease.
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MESH Headings
- Animals
- Base Sequence
- Chromosome Mapping
- Deafness/chemically induced
- Deafness/genetics
- Disease Models, Animal
- Ethylnitrosourea/analogs & derivatives
- Female
- Genes, Recessive
- Genetic Testing
- Hair Cells, Auditory, Outer/cytology
- Hair Cells, Auditory, Outer/pathology
- Hair Cells, Auditory, Outer/physiology
- Humans
- Male
- Membrane Proteins/genetics
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Mutagens
- Neoplasm Proteins/metabolism
- Pedigree
- Point Mutation
- Psychomotor Agitation/genetics
- Sequence Alignment
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Affiliation(s)
- Martin Schwander
- Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037
| | - Anna Sczaniecka
- Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037
| | - Nicolas Grillet
- Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037
| | - Janice S. Bailey
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Matthew Avenarius
- Department of Otolaryngology and the Interdepartmental Ph.D. Genetic Program, The University of Iowa, Iowa City, Iowa 52242
| | - Hossein Najmabadi
- Genetic Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran
| | - Brian M. Steffy
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Glenn C. Federe
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Erica A. Lagler
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Raheleh Banan
- Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037
| | - Rudy Hice
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | | | - Elisabeth M. Keithley
- Departments of Surgery and Neurosciences, University of California, San Diego School of Medicine and Veterans Affairs Medical Center, La Jolla, California 92093, and
| | - Allen F. Ryan
- Departments of Surgery and Neurosciences, University of California, San Diego School of Medicine and Veterans Affairs Medical Center, La Jolla, California 92093, and
| | - Gary D. Housley
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Tim Wiltshire
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Richard J. H. Smith
- Department of Otolaryngology and the Interdepartmental Ph.D. Genetic Program, The University of Iowa, Iowa City, Iowa 52242
| | - Lisa M. Tarantino
- Genomics Institute of the Novartis Research Foundation, San Diego, California 92121
| | - Ulrich Müller
- Department of Cell Biology, Institute for Childhood and Neglected Disease, The Scripps Research Institute, La Jolla, California 92037
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16
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Kitamoto J, Libby RT, Gibbs D, Steel KP, Williams DS. Myosin VI is required for normal retinal function. Exp Eye Res 2005; 81:116-20. [PMID: 15978262 DOI: 10.1016/j.exer.2005.02.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 02/22/2005] [Indexed: 11/18/2022]
Abstract
Different unconventional myosins have been shown to play important roles in sensory function, including vision. We investigated the role of myosin VI by examining the retinas of mice carrying a null mutation in the myosin VI gene. Myosin VI was found to be present in the photoreceptor and RPE cells of normal retinas. In the absence of myosin VI, the amplitudes of the a- and b-waves of the electroretinogram were reduced, although there was not photoreceptor cell loss and retinal anatomy appeared normal. Our results indicate that myosin VI is required in photoreceptor cells for normal retinal electrophysiology.
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Affiliation(s)
- Junko Kitamoto
- Department of Pharmacology, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
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17
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Abstract
Myosin motor proteins use the energy derived from ATP hydrolysis to move cargo along actin tracks. Myosin VI, unlike almost all other myosins, moves toward the minus end of actin filaments and functions in a variety of intracellular processes such as vesicular membrane traffic, cell migration, and mitosis. These diverse roles of myosin VI are mediated by interaction with a number of different binding partners present in multi-protein complexes. Myosin VI can work in vitro as a processive dimeric motor and as a nonprocessive monomeric motor, each with a large working stroke. The possibility that both monomeric and dimeric forms of myosin VI operate in the cell may represent an important regulatory mechanism for controlling the multiple steps in transport pathways where nonprocessive and processive motors are required.
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Affiliation(s)
- Folma Buss
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge CB2 2XY, United Kingdom.
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18
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Seiler C, Ben-David O, Sidi S, Hendrich O, Rusch A, Burnside B, Avraham KB, Nicolson T. Myosin VI is required for structural integrity of the apical surface of sensory hair cells in zebrafish. Dev Biol 2004; 272:328-38. [PMID: 15282151 DOI: 10.1016/j.ydbio.2004.05.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2004] [Revised: 04/30/2004] [Accepted: 05/04/2004] [Indexed: 10/26/2022]
Abstract
Unconventional myosins have been associated with hearing loss in humans, mice, and zebrafish. Mutations in myosin VI cause both recessive and dominant forms of nonsyndromic deafness in humans and deafness in Snell's waltzer mice associated with abnormal fusion of hair cell stereocilia. Although myosin VI has been implicated in diverse cellular processes such as vesicle trafficking and epithelial morphogenesis, the role of this protein in the sensory hair cells remains unclear. To investigate the function of myosin VI in zebrafish, we cloned and examined the expression pattern of myosin VI, which is duplicated in the zebrafish genome. One duplicate, myo6a, is expressed in a ubiquitous pattern during early development and at later stages, and is highly expressed in the brain, gut, and kidney. myo6b, on the other hand, is predominantly expressed in the sensory epithelium of the ear and lateral line at all developmental stages examined. Both molecules have different splice variants expressed in these tissues. Using a candidate gene approach, we show that myo6b is satellite, a gene responsible for auditory/vestibular defects in zebrafish larvae. Examination of hair cells in satellite mutants revealed that stereociliary bundles are irregular and disorganized. At the ultrastructural level, we observed that the apical surface of satellite mutant hair cells abnormally protrudes above the epithelium and the membrane near the base of the stereocilia is raised. At later stages, stereocilia fused together. We conclude that zebrafish myo6b is required for maintaining the integrity of the apical surface of hair cells, suggesting a conserved role for myosin VI in regulation of actin-based interactions with the plasma membrane.
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Affiliation(s)
- Christoph Seiler
- Max-Planck-Institut fur Entwicklungsbiologie, 72076 Tubingen, Germany
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19
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Kappler JA, Starr CJ, Chan DK, Kollmar R, Hudspeth AJ. A nonsense mutation in the gene encoding a zebrafish myosin VI isoform causes defects in hair-cell mechanotransduction. Proc Natl Acad Sci U S A 2004; 101:13056-61. [PMID: 15317943 PMCID: PMC516516 DOI: 10.1073/pnas.0405224101] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In a three-generation screen of chemically mutagenized zebrafish, we identified a group of mutations that affect the development and function of hair cells, the mechanically sensitive cells of the inner ear and lateral-line organ. One mutant line, ru920, was discovered in a behavioral screen for defects in the acoustically evoked escape response. Despite apparently normal numbers of hair cells, mutants lack an inner-ear microphonic potential and exhibit reduced labeling of hair cells by a fluorophore that traverses transduction channels. This hair-cell-specific phenotype suggested a defect in the mechanoelectrical transduction apparatus. Positional cloning revealed that the recessive mutation introduces a premature stop codon in the ORF of myosin6b (myo6b), one of the two zebrafish orthologs of the human gene myosin VI. The ru920 line therefore provides an animal model with which to study the role of class VI myosin proteins in mechanotransduction.
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Affiliation(s)
- James A Kappler
- Howard Hughes Medical Institute, Laboratory of Sensory Neuroscience, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA
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20
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Swiatecka-Urban A, Boyd C, Coutermarsh B, Karlson KH, Barnaby R, Aschenbrenner L, Langford GM, Hasson T, Stanton BA. Myosin VI regulates endocytosis of the cystic fibrosis transmembrane conductance regulator. J Biol Chem 2004; 279:38025-31. [PMID: 15247260 DOI: 10.1074/jbc.m403141200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cystic fibrosis transmembrane conductance regulator (CFTR) is a cyclic AMP-regulated Cl(-) channel expressed in the apical plasma membrane in fluid-transporting epithelia. Although CFTR is rapidly endocytosed from the apical membrane of polarized epithelial cells and efficiently recycled back to the plasma membrane, little is known about the molecular mechanisms regulating CFTR endocytosis and endocytic recycling. Myosin VI, an actin-dependent, minus-end directed mechanoenzyme, has been implicated in clathrin-mediated endocytosis in epithelial cells. The goal of this study was to determine whether myosin VI regulates CFTR endocytosis. Endogenous, apical membrane CFTR in polarized human airway epithelial cells (Calu-3) formed a complex with myosin VI, the myosin VI adaptor protein Disabled 2 (Dab2), and clathrin. The tail domain of myosin VI, a dominant-negative recombinant fragment, displaced endogenous myosin VI from interacting with Dab2 and CFTR and increased the expression of CFTR in the plasma membrane by reducing CFTR endocytosis. However, the myosin VI tail fragment had no effect on the recycling of endocytosed CFTR or on fluid-phase endocytosis. CFTR endocytosis was decreased by cytochalasin D, an actin-filament depolymerizing agent. Taken together, these data indicate that myosin VI and Dab2 facilitate CFTR endocytosis by a mechanism that requires actin filaments.
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21
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Jiang S, Ramachandran S. Identification and Molecular Characterization of Myosin Gene Family in Oryza sativa Genome. ACTA ACUST UNITED AC 2004; 45:590-9. [PMID: 15169941 DOI: 10.1093/pcp/pch061] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Myosins play an important role in various developmental processes in plants. We have identified 14 myosin genes in rice (Oryza sativa cv. Nipponbare) genome using sequence information available in public databases. Phylogenetic analysis of these sequences with other plant and non-plant myosins revealed that two of the predicted sequences belonged to class VIII and the others to class XI. All of these genes were distributed on seven chromosomes in the rice genome. Domain searches on these sequences indicated that a typical rice myosin consisted of Myosin_N, head domain, neck (IQ motifs), tail, and dilute (DIL) domain. Based on the sequence information obtained from predicted myosins, we isolated and sequenced two full-length cDNAs, OsMyoVIIIA and OsMyoXIE, representing each of the two classes of myosins. These two cDNAs isolated from different organs existed in isoforms due to differential splicing and showed minor differences from the predicted myosin in exon organization. Out of 14 myosin genes 11 were expressed in three major organs: leaves, panicles, and roots, among which three myosins exhibited different expression levels. On the other hand, three of the total myosin sequences showed organ-specific expression. The existence of different myosin genes and their isoforms in different organs or tissues indicates the diversity of myosin functions in rice.
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Affiliation(s)
- ShuYe Jiang
- Rice Functional Genomics Group, Temasek Life Sciences Laboratory, 1 Research Link, the National University of Singapore, Singapore 117604
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22
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Abstract
Actin is found at the cortex of the cell where endocytosis occurs, but does it play a role in this essential process? Recent studies on the unconventional myosin, myosin VI, an actin-based molecular motor, provide compelling evidence that this myosin and therefore actin is involved in two distinct steps of endocytosis in higher eukaryotes: the formation of clathrin-coated vesicles and the movement of nascent uncoated vesicles from the actin-rich cell periphery to the early endosome. Three distinct adapter proteins--GIPC, Dab2 and SAP97--that associate with the cargo-binding tail domain of myosin VI have been identified. These proteins may recruit myosin VI to its sites of action.
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Affiliation(s)
- Tama Hasson
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California at San Diego, 2129 Bonner Hall, MC 0368, 9500 Gilman Drive, La Jolla, CA 92093-0368, USA.
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23
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Aschenbrenner L, Lee T, Hasson T. Myo6 facilitates the translocation of endocytic vesicles from cell peripheries. Mol Biol Cell 2003; 14:2728-43. [PMID: 12857860 PMCID: PMC165672 DOI: 10.1091/mbc.e02-11-0767] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Immunolocalization studies in epithelial cells revealed myo6 was associated with peripherally located vesicles that contained the transferrin receptor. Pulse-chase experiments after transferrin uptake showed that these vesicles were newly uncoated endocytic vesicles and that myo6 was recruited to these vesicles immediately after uncoating. GIPC, a putative myo6 tail binding protein, was also present. Myo6 was not present on early endosomes, suggesting that myo6 has a transient association with endocytic vesicles and is released upon early endosome fusion. Green fluorescent protein (GFP) fused to myo6 as well as the cargo-binding tail (M6tail) alone targeted to the nascent endocytic vesicles. Overexpression of GFP-M6tail had no effect on a variety of organelle markers; however, GFP-M6tail displaced the endogenous myo6 from nascent vesicles and resulted in a significant delay in transferrin uptake. Pulse-chase experiments revealed that transferrin accumulated in uncoated vesicles within the peripheries of transfected cells and that Rab5 was recruited to the surface of these vesicles. Given sufficient time, the transferrin did traffic to the perinuclear sorting endosome. These data suggest that myo6 is an accessory protein required for the efficient transportation of nascent endocytic vesicles from the actin-rich peripheries of epithelial cells, allowing for timely fusion of endocytic vesicles with the early endosome.
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Affiliation(s)
- Laura Aschenbrenner
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, California 92093, USA
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24
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Ahmed ZM, Morell RJ, Riazuddin S, Gropman A, Shaukat S, Ahmad MM, Mohiddin SA, Fananapazir L, Caruso RC, Husnain T, Khan SN, Riazuddin S, Griffith AJ, Friedman TB, Wilcox ER. Mutations of MYO6 are associated with recessive deafness, DFNB37. Am J Hum Genet 2003; 72:1315-22. [PMID: 12687499 PMCID: PMC1180285 DOI: 10.1086/375122] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2003] [Accepted: 02/25/2003] [Indexed: 11/03/2022] Open
Abstract
Cosegregation of profound, congenital deafness with markers on chromosome 6q13 in three Pakistani families defines a new recessive deafness locus, DFNB37. Haplotype analyses reveal a 6-cM linkage region, flanked by markers D6S1282 and D6S1031, that includes the gene encoding unconventional myosin VI. In families with recessively inherited deafness, DFNB37, our sequence analyses of MYO6 reveal a frameshift mutation (36-37insT), a nonsense mutation (R1166X), and a missense mutation (E216V). These mutations, along with a previously published missense allele linked to autosomal dominant progressive hearing loss (DFNA22), provide an allelic spectrum that probes the relationship between myosin VI dysfunction and the resulting phenotype.
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Affiliation(s)
- Zubair M. Ahmed
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Robert J. Morell
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Saima Riazuddin
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Andrea Gropman
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Shahzad Shaukat
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Mussaber M. Ahmad
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Saidi A. Mohiddin
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Lameh Fananapazir
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Rafael C. Caruso
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Tayyab Husnain
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Shaheen N. Khan
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Sheikh Riazuddin
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Andrew J. Griffith
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Thomas B. Friedman
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
| | - Edward R. Wilcox
- Section on Human Genetics, Section on Gene Structure and Function, Laboratory of Molecular Genetics, and Hearing Section, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Rockville, MD; National Center of Excellence in Molecular Biology, Punjab University, Lahore, Pakistan; Neurogenetics Branch, National Institute of Neurological Disorders and Stroke, and Department of Neurology, Children’s National Medical Center, Washington, D.C.; and Clinical Cardiology Section, National Heart, Lung and Blood Institute, and Section on Ophthalmic Molecular Genetics, National Eye Institute, National Institutes of Health, Bethesda
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25
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Morris SM, Arden SD, Roberts RC, Kendrick-Jones J, Cooper JA, Luzio JP, Buss F. Myosin VI binds to and localises with Dab2, potentially linking receptor-mediated endocytosis and the actin cytoskeleton. Traffic 2002; 3:331-41. [PMID: 11967127 DOI: 10.1034/j.1600-0854.2002.30503.x] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Myosin VI, an actin-based motor protein, and Disabled 2 (Dab2), a molecule involved in endocytosis and cell signalling, have been found to bind together using yeast and mammalian two-hybrid screens. In polarised epithelial cells, myosin VI is known to be associated with apical clathrin-coated vesicles and is believed to move them towards the minus end of actin filaments, away from the plasma membrane and into the cell. Dab2 belongs to a group of signal transduction proteins that bind in vitro to the FXNPXY sequence found in the cytosolic tails of members of the low-density lipoprotein receptor family. The central region of Dab2, containing two DPF motifs, binds to the clathrin adaptor protein AP-2, whereas a C-terminal region contains the binding site for myosin VI. This site is conserved in Dab1, the neuronal counterpart of Dab2. The interaction between Dab2 and myosin VI was confirmed by in vitro binding assays and coimmunoprecipitation and by their colocalisation in clathrin-coated pits/vesicles concentrated at the apical domain of polarised cells. These results suggest that the myosin VI-Dab2 interaction may be one link between the actin cytoskeleton and receptors undergoing endocytosis.
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Affiliation(s)
- Shelli M Morris
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109-1024, USA
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26
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Abstract
Functional activities of many nonmuscle myosin isoforms are (or are postulated to be) regulated by heavy chain phosphorylation. Depending on the myosin isoform, the serine or threonine residues located within the head (myosin I or myosin VI) or within the C-terminal tail domains (myosin II or myosin V) can be phosphorylated by more or less specific endogenous kinases. In some isoforms phosphorylation can occur both in the head and tail domains, as it has been found for myosin III. There are also isoforms that can be regulated both by the heavy and regulatory light chain phosphorylation, as for the example myosin II from slide mold Dictyostelium discoideum. The goal of this review was to describe recent findings on regulation of myosin I, myosin II, myosin III, myosin V and myosin VI isoforms by their heavy chain phosphorylation including the short charcteristics of the relevant kinases. The biological aspects of the phosphorylation are also discussed.
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Affiliation(s)
- M J Redowicz
- Department of Muscle Biochemistry, Nencki Institute of Experimental Biology, Warsaw, Poland.
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27
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Abstract
The integrity of the actin cytoskeleton and associated motor proteins are essential for the efficient functioning of clathrin mediated endocytosis at least in polarised cells. Myosin VI, the only motor protein so far identified that moves towards the minus end of actin filaments, is the first motor protein to be shown to associate with clathrin coated pits/vesicles at the plasma membrane and to modulate clathrin mediated endocytosis. Recent kinetic studies suggest that myosin VI may move processively along actin filaments providing clues about its functions in the cell. The possible role(s) of myosin VI in the sequential steps involved in receptor mediated endocytosis are discussed.
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Affiliation(s)
- F Buss
- Department of Clinical Biochemistry, University of Cambridge, UK.
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28
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Lloyd RV, Vidal S, Jin L, Zhang S, Kovacs K, Horvath E, Scheithauer BW, Boger ET, Fridell RA, Friedman TB. Myosin XVA expression in the pituitary and in other neuroendocrine tissues and tumors. THE AMERICAN JOURNAL OF PATHOLOGY 2001; 159:1375-82. [PMID: 11583965 PMCID: PMC1850513 DOI: 10.1016/s0002-9440(10)62524-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The myosin superfamily of molecular motor proteins includes conventional myosins and several classes of unconventional myosins. Recent studies have characterized the human and mouse unconventional myosin XVA, which has a role in the formation and/or maintenance of the unique actin-rich structures of inner ear sensory hair cells. Myosin XVA is also highly expressed in human anterior pituitary cells. In this study we examined the distribution of myosin XVA protein and mRNA in normal and neoplastic human pituitaries and other neuroendocrine cells and tumors. Myosin XVA was expressed in all types of normal anterior pituitary cells and pituitary tumors and in other neuroendocrine cells and tumors including those of the adrenal medulla, parathyroid, and pancreatic islets. Most nonneuroendocrine tissues examined including liver cells were negative for myosin XVA protein and mRNA, although the distal and proximal tubules of normal kidneys showed moderate immunoreactivity for myosin XVA. Ultrastructural immunohistochemistry localized myosin XVA in association with secretory granules of human anterior pituitary cells and human pituitary tumors. These data suggest that in neuroendocrine cells myosin XVA may have a role in secretory granule movement and/or secretion.
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Affiliation(s)
- R V Lloyd
- Mayo Clinic and Mayo Foundation, Rochester, Minnesota 55905, USA.
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29
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Buss F, Arden SD, Lindsay M, Luzio J, Kendrick-Jones J. Myosin VI isoform localized to clathrin-coated vesicles with a role in clathrin-mediated endocytosis. EMBO J 2001; 20:3676-84. [PMID: 11447109 PMCID: PMC125554 DOI: 10.1093/emboj/20.14.3676] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Myosin VI is involved in membrane traffic and dynamics and is the only myosin known to move towards the minus end of actin filaments. Splice variants of myosin VI with a large insert in the tail domain were specifically expressed in polarized cells containing microvilli. In these polarized cells, endogenous myosin VI containing the large insert was concentrated at the apical domain co-localizing with clathrin- coated pits/vesicles. Using full-length myosin VI and deletion mutants tagged with green fluorescent protein (GFP) we have shown that myosin VI associates and co-localizes with clathrin-coated pits/vesicles by its C-terminal tail. Myosin VI, precipitated from whole cytosol, was present in a protein complex containing adaptor protein (AP)-2 and clathrin, and enriched in purified clathrin-coated vesicles. Over-expression of the tail domain of myosin VI containing the large insert in fibroblasts reduced transferrin uptake in transiently and stably transfected cells by >50%. Myosin VI is the first motor protein to be identified associated with clathrin-coated pits/vesicles and shown to modulate clathrin-mediated endocytosis.
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Affiliation(s)
- Folma Buss
- Department of Clinical Biochemistry and Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2XY and
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding author e-mail:
| | | | | | | | - John Kendrick-Jones
- Department of Clinical Biochemistry and Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2XY and
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding author e-mail:
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30
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Cramer LP. Myosin VI: roles for a minus end-directed actin motor in cells. J Cell Biol 2000; 150:F121-6. [PMID: 10995456 PMCID: PMC2150707 DOI: 10.1083/jcb.150.6.f121] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2000] [Accepted: 08/16/2000] [Indexed: 11/22/2022] Open
Affiliation(s)
- L P Cramer
- MRC-Laboratory Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.
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31
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Abstract
Members of the myosin superfamily of actin-based motor proteins were previously thought to move only towards the barbed end of the actin filament. In an extraordinary reversal of this dogma, an abundant and widespread unconventional myosin known as myosin VI has recently been shown to move towards the pointed end of the actin filament - the opposite direction of all other characterized myosins. This discovery raises novel and intriguing questions about the molecular mechanisms of reversal and the biological roles of this 'backwards' myosin.
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Affiliation(s)
- O C Rodriguez
- Dept of Cell and Molecular Physiology, School of Medicine, University of North Carolina at Chapel Hill, 27599-7545, USA
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32
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Abstract
Myosins constitute a large superfamily of actin-dependent molecular motors. Phylogenetic analysis currently places myosins into 15 classes. The conventional myosins which form filaments in muscle and non-muscle cells form class II. There has been extensive characterization of these myosins and much is known about their function. With the exception of class I and class V myosins, little is known about the structure, enzymatic properties, intracellular localization and physiology of most unconventional myosin classes. This review will focus on myosins from class IV, VI, VII, VIII, X, XI, XII, XIII, XIV and XV. In addition, the function of myosin II in non-muscle cells will also be discussed.
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Affiliation(s)
- J R Sellers
- National Heart, Lung and Blood Institute, National Institutes of Health, Building 10, Room 8N202, Bethesda, MD 20892, USA.
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